add oversaturate_only mark

conftest.py

@@ -1,8 +1,11 @@
-# https://pytest.org/latest/example/simple.html#control-skipping-of-tests-according-to-command-line-option
 from __future__ import annotations
 
+import math
+
 import pytest
 
+import dask
+
 # Uncomment to enable more logging and checks
 # (https://docs.python.org/3/library/asyncio-dev.html)
 # Note this makes things slower and might consume much memory.
@@ -27,13 +30,24 @@ def pytest_addoption(parser):
 
 
 def pytest_collection_modifyitems(config, items):
-    if config.getoption("--runslow"):
+    # https://pytest.org/latest/example/simple.html#control-skipping-of-tests-according-to-command-line-option
+    if skip_slow := not config.getoption("--runslow"):
         # --runslow given in cli: do not skip slow tests
-        return
-    skip_slow = pytest.mark.skip(reason="need --runslow option to run")
+        skip_slow_marker = pytest.mark.skip(reason="need --runslow option to run")
+
+    if skip_oversaturate := math.isfinite(
+        dask.config.get("distributed.scheduler.worker_saturation")
+    ):
+        skip_oversaturate_marker = pytest.mark.skip(
+            reason="need `distributed.scheduler.worker_saturation = inf` to run"
+        )
+
     for item in items:
-        if "slow" in item.keywords:
-            item.add_marker(skip_slow)
+        if skip_slow and "slow" in item.keywords:
+            item.add_marker(skip_slow_marker)
+
+        if skip_oversaturate and "oversaturate_only" in item.keywords:
+            item.add_marker(skip_oversaturate_marker)
 
         if "ws" in item.fixturenames:
             item.add_marker(pytest.mark.workerstate)

setup.cfg

@@ -99,6 +99,7 @@ markers =
     gpu: marks tests we want to run on GPUs
     leaking: ignore leaked resources; see pytest_resourceleaks.py for usage
     workerstate: deterministic test for the worker state machine. Automatically applied to all tests that use the 'ws' fixture.
+    oversaturate_only: tests that only work/make sense to run if root task queuing is disabled
 
 # pytest-timeout settings
 # 'thread' kills off the whole test suite. 'signal' only kills the offending test.